Introduction: High-dose chemotherapy with autologous stem-cell transplantation (HDC-ASCT) is now the preferred consolidation strategy for young PCNSL patients. The optimal conditioning regimen is unknown. The data suggests that BEAM (carmustine, etoposide, cytarabine, melphalan) is ineffective, BCNU/TT (carmustine/thiotepa) is well-tolerated with treatment related mortality (TRM) 1%–3%, but late relapses are common, and TBC (thiotepa, busulfan, cyclophosphamide) is highly effective but with higher TRM 11%. Methods: The aim of the study was to analyze the safety and efficacy of consolidation based on conditioning regimen consisted of carmustine, etoposide and thiotepa (BET)1 followed by ASCT. We evaluated the outcome of 45 immunocompetent adult patients with PCNSL treated in 4 Polish centers between Feb. 2015 and Oct. 2022. Six cycles of induction with rituximab, methotrexate (3.5 g/m2), ifosfamide and vincristine (R-MIV) and one cycle of cytarabine with thiotepa (AT)2 were given. Patients with a complete or partial response (CR/PR) proceeded to consolidation with carmustine 400 mg/m2 on day -5, etoposide 150 mg/m2 on day -5,-4, -3, and thiotepa 5 mg/kg every 12 h on days -4 and -3 (total 4 doses), followed by ASCT. Results: Median age (range) of 45 transplanted patients was 57 years (19-66) with 15 (33%) patients ≥60 years old. At the end of induction 29 (64.5%) patients obtained CR/CRun (19/10 respectively), with additional 5 (11%) patients with no evidence of disease at baseline, and 11 (24.5%) in PR, based on standard CT/MRI assessment. For 32 (71%) patients with 18FDG PET/CT done before ASCT, metabolic-CR was confirmed. Mean (range) number of 584.4 (187–2642) × 106 CD34+ peripheral blood stem cells were collected, corresponding to 7.2 × 106 cells/kg (2.55–34.7 × 106 cells/kg). Mean hospitalization time from the day of ASCT was 15 days. Mean time to hematologic recovery with PLT > 25 G/L and NEU > 0.5/ > 1.0 G/L was 9 and 9/10 days, respectively. The most common grade 3–4 non-haematological toxicities were diarrhea (12 patients, mean 4 days) and mucositis (18 patients, mean 5 days). Febrile neutropenia occurred in 21 patients (mean 2.5 days). Blood cultures did not reveal any relevant pathogens except one patient with confirmed Enterobacter cloacae-ESBL and Klebsiella oxytoca. Two patients (TRM 4.4%) died of transplant-related complications: septic shock and neurotoxicity. At a median (range) follow-up of 41 (13-92) months, 3-year progression free survival (PFS) and overall survival (OS) was 78% (95% CI: 65-91) and 81% (95% CI: 68-93). Relapse occurred in 9 patients, in all but one within first 11 months after ASCT. Causes of death were: lymphoma progression (n = 6), TRM (n = 2), accident (n = 1) and concomitant diseases (n = 2). Keywords: aggressive B-cell non-Hodgkin lymphoma, stem cell transplant No conflicts of interests pertinent to the abstract.
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